两条SQL语句:
(1)select * from user;
(2)select id,name from user where id like %%;
注:user表中只有id,name字段这两条sql有什么区别?
(1)select * from user;
(2)select id,name from user where id like %%;
注:user表中只有id,name字段这两条sql有什么区别?
第二条不能选出ID是null的数据。
select id,name from user where id like %%;
等同于
select id,name from user where id is not null;